1. Field of the Invention
The invention relates to an adapter chainring for a conventional road racing bicycle crankset and, more particularly, to an adapter chainring for converting a conventional crankset having two chainrings to a crankset having three chainrings, including an additional smaller inner chainring. The invention allows the road racing crankset to be converted for applications requiring the very low gear ratios provided by the additional chainring.
2. Discussion of the Related Art
Bicycle cranksets having two and three chainrings have been known in the prior art. Two chainring cranksets comprise an outer, large diameter chainring and an inner, smaller diameter chainring. These cranksets may be used in combination with 5, 6, 7 and 8 speed freewheels, thus providing the bicycle with a range of from 10 to 16 speeds. Two chainring cranksets are commonly used in road racing bicycles which are primarily designed for road racing applications.
Three chainring cranksets comprise an outer, large chainring; a middle, smaller diameter chainring; and an inner, still smaller diameter chainring. They are used in bicycling applications where still lower gears are required, such as in touring and off-road bicycles referred to as "mountain bikes." These bicycles may have as many as 24 gears due to the additional third chainring. Consequently, these bicycles are ideally suited for climbing steep elevations and maneuvering on rugged off-road terrain where the very lowest gears are required.
The above-described prior art two and three chainring cranksets are, however, essentially limited in their utility to the specific applications for which they were designed. More particularly, road racing bicycles having two chainring cranksets are poorly suited for touring and off-road uses.